ES2602090T3 - Procedure to treat a surface of a substrate - Google Patents

Abstract

Method for treating a surface of a substrate, said method comprising applying a functional chemical substance on the surface of the substrate to improve the adhesion of the silicone to said substrate, wherein the method comprises: - applying said functional chemical substance in an amount of at least 5 mg/m2 on the surface of the substrate using a vapor application beam to form a functional chemical layer on the substrate, said functional chemical comprising double bonds, silane hydride, or vinylsilane reactive groups, or oligomeric or polymeric hydrocarbon or polysiloxane compounds.

Description

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DESCRIPTION

Procedure to treat a surface of a substrate.

The present invention relates to a process for treating a surface of a substrate to improve the adhesion of silicone to the substrate and thereby prevent the elimination of silicone by rubbing. The method comprises applying a functional chemical substance on the substrate surface using a vapor application beam to form a layer of functional chemical substance on the substrate to improve the adhesion of the silicone to said substrate. The invention also relates to a release coating comprising a substrate treated with the method according to the invention.

Release coatings, such as silicone coatings, have been used to enhance the release properties of a substrate, such as paper, film or plastic coated paper substrate. The silicone coating may form a release layer for a release coating, or the silicone coating may be, for example, a functional layer of waxed baking paper.

In the case of release linings, in which silicone is applied on the surface of the substrate, the adhesion at the interface of these two layers may continue to be too weak, resulting in delamination problems. Therefore, when paper or other silicone-coated substrates are produced, a good adhesion of the silicone and poor removal by rubbing is desired. In addition, special attention should be given to the quality of the non-siliconized base material in order to minimize the amount of the silicone coating.

Typically, attempts have been made to improve the adhesion of the silicone by mixing some additives in the silicone. Functional chemical substances have also been developed, which can prevent the removal of silicone by rubbing by anchoring the silicone to a surface of the substrate. The structure of these functional chemical substances comprises a residue or moieties that are compatible with the substrate, and a moiety or moieties that are reactive or at least compatible with the silicone coating. The functional chemical substance may comprise at least one block copolymer or functionalized graft at the end or on one side with groups capable of reacting with the silicone. The functional chemical substance can also be a copolymer containing groups after polymerization capable of reacting with the silicone. Therefore, functional chemical substances are capable of forming covalent bonds at the interface between the silicone and the substrate, and thus the adhesion of the silicone can be improved.

A problem with the functional chemical substances described above is that they involve high costs, and therefore can only be used commercially in low addition ratios. If these functional chemical substances are mixed in a coating agent or surface sizing and applied on the substrate surface with a usual coating equipment, only a small proportion of the functional chemical substance meets the surface of the substrate. This leads to a high consumption of the functional chemical substance, and possibly a non-homogeneous adhesion of the silicone.

Therefore, there is a need for a new procedure to treat the surface of a substrate with a very small amount of functional chemical substance, which results in considerable cost savings. In addition, the new application procedure should create a uniform layer of the chemical substance on the surface of the substrate in order to achieve desired functionality.

The aim of the present invention is to provide a new method for treating a surface of the substrate in such a way that the functional chemical substance is needed only at low coating weights, so that the removal of silicone by rubbing can be avoided.

To achieve these objectives, the method according to the invention for treating a surface of a substrate to improve the adhesion of silicone to a substrate is characterized in the first place by the fact that the method comprises:

- applying said functional chemical substance in an amount of at least 5 mg / m2 on the substrate surface using a vapor application beam to form a layer of functional chemical substance on the substrate, functional chemical substance which comprises vinyl reactive groups, of silane hydride, or of vinyl silane or double bonds, preferably terminal or lateral groups, or oligomeric or polymeric hydrocarbon or polysiloxanic compounds.

The basic idea of the method according to the invention is to create a thin functional layer on the surface of a substrate to improve the characteristics of the substrate surface that are necessary for the continued treatment of the substrate with silicone. The thin functional layer just between the substrate and the silicone layer improves the adhesion of the silicone.

The method according to the invention uses high-speed steam to distribute water-soluble, water dispersible or water emulsifiable functional chemical substances on the surface of the substrate. The procedure is carried out by means of a steam application beam that has a specific nozzle system and the capacity

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to apply a functional chemical substance or substances in aqueous form with steam. The nozzle system in the steam applicator is designed to create a good mixing efficiency of the steam and of the functional chemical substance or substances. The nozzle system feeds the dissolution of the functional chemical substance or substances in a vapor flow in the application chamber, in which a very fine mist of functional chemical substance or substances is formed. The small size of the droplets of the solution of functional chemical substance gives the possibility of applying a uniform layer on the surface of the substrate at a low coating weight.

The steam applicator preferably used in the process according to the invention is a commercial solution of HU Jakob Papiertechnik AG, Switzerland, which has been presented in patent publication W02007 / 003059. This steam applicator is mainly used to apply steam in which water is applied to increase the moisturizing effect. Now, it has been discovered that this type of steam application beam presented by the specific nozzle system can also be used to treat the surface of the substrate with functional chemical substances in order to form the thin functional layer just above the outermost surface of the substratum. However, the invention is not limited to the use of this particular steam application beam, but other steam application beams that provide the same type of distribution procedure are also applicable.

The layer of functional chemical substance formed using the steam application beam comprises at least 5 mg / m2 of the functional chemical substance. Preferably, the coating weight is approximately 0.05 g / m2, but depending on the subsequent processing of the substrate and the final use of the treated substrate, the coating weight may also be above 0.05 g / m2. Using this steam application beam it is possible to form this type of low weight functional layer.

The substrate can be an uncoated substrate or a previously coated substrate. The substrate is made of paper, film material (plastic), or paper coated with film (plastic). The paper substrate can be coated, pressed or surface treated in another way. The paper substrate may also be calendered or not calendered. The film material substrate may be made of a thermoplastic polymeric material, advantageously ethylene polyterephthalate (PET), oriented polypropylene (OPP), low density polyethylene (LDPE), or high density polyethylene (HDPE).

The improvement in adhesion is based on the structure of a functional chemical substance that is applied to the substrate. The functional chemical substance may be a functional polymer or a low molecular weight chemical substance, which comprises a moiety or moieties that are compatible with the substrate, and a moiety or moieties that are reactive or at least compatible with the silicone coating. The functional chemical substance may make possible a covalent bond between the silicone coating and the surface of the functional layer. The functional chemical substances used in the process according to the invention are applied on the surface of the substrate in water in the form of a solution, a dispersion or an emulsion, and the chemical substance is selected on the basis of the silicone coating and the end use of the base material.

The steam beam technique described above allows the application of functional chemical substances precisely on the outermost surface of the substrate, which is needed to create a strong interaction with another layer such as silicone. The method according to the invention makes it possible to treat a substrate web, for example the base paper web of a release liner, during papermaking, and thus the base paper comprising the functional layer can be supplied to the manufacturers of the release paper and do not need to use any additives to improve the adhesion of the coatings.

The invention was particularly developed to improve adhesion at the interface of the silicone layer and the substrate in the case of release coatings. But other uses are also possible, in which a good silicone adhesion is required. In addition, the invention also developed from the point of view of specific functional chemical substances that cannot be used in industrial applications due to economic reasons, if conventional coating procedures are used. The method according to the invention is suitable for all water soluble or water dispersible functional chemical substances, and is not limited to the chemical substances presented in this description.

Next, the invention will be described by examples, and will be illustrated with reference to the drawings, in which

Figure 1 represents the structure of a release liner comprising a substrate treated with the method according to the invention, and

Figure 2 represents some polymeric structures of the functional chemical substance, which can be applied on the surface of the substrate by the method according to the invention.

Figure 1 represents a structure of a release liner 5, which is made from a substrate 1 treated with the method according to the invention. The release liner 5 comprises the substrate 1, a functional layer 2 on the surface of the substrate, and a coating layer 3 on top of the functional layer 2. The substrate

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refers to a paper substrate, a film substrate (plastic), or a paper substrate coated with film (plastic). The paper substrate may be coated, pressed or otherwise superficially treated (not shown in Figure 1). The coating layer 3 refers to a silicone coating, and the functional layer 2 comprises the functional chemical substance that is capable of reacting with a silicone or that is compatible with silicone. In many cases, the crosslinking of the silicone coating 3 is based on the hydrosilylation reaction between the double bonds and the silane hydride groups in the presence of platinum catalyst. During crosslinking, silicone reactive groups can also react strongly with the functional layer. The silicone coating can be based, for example, on a solvent-containing silicone, a solvent-free silicone, a UV cured silicone, or an emulsion silicone.

The present invention provides a new process for forming a layer 2 of functional chemical substance on the surface of the substrate 1. When the functional chemical substance is applied on a substrate, a base material 4 is formed. The base material 4, which comprises substrate 1 and a functional layer 2, can be manufactured separately from the silicone coating process.

A layer of functional chemical substance is formed using a vapor application beam such that a solution of functional chemical substance is mixed with the vapor. The concentration of the functional chemical substance, for example in the case of a polymer solution, is below 15% by weight. Preferably, the concentration is below 4% by weight. The operating conditions of the steam application beam are as normally used. The operating temperature of the steam application beam is approximately 90 to 120 ° C, and the vapor pressure is approximately 1 to 1.5 bar.

The steam application beam nozzles apply the solution of functional chemical substance on the substrate band continuously, and a uniform thin functional layer can be formed.

The functionalized chemical substances distributed in the process according to the invention to the surface of the substrate may be polymeric functional chemical substances, which comprise at least one block copolymer or functionalized graft at the end or on the side with groups that can react with a silicone or groups that are compatible with silicone.

The functional chemical substance may also be a low molecular weight functional chemical substance comprising a residue or residues that are reactive or compatible with silicone and a residue or residues that are reactive or compatible with a substrate surface. In this case, the concentration of the functional chemical substance in the solution may be greater than 15% by weight.

Figure 2 depicts some advantageous polymeric structures of the functional chemical substance that can be used as a functional layer to provide better adhesion between the silicone coating and the substrate. The release coating comprises a substrate 1, a functional layer 2, and a coating layer 3. Adhesion of the coating layer to the substrate can be improved using functionalized polymers comprising both a moiety 14 that is compatible with the substrate and a moiety 15-19 that is reactive or compatible with silicone coating 3. The reactive moiety preferably contains vinyl terminal or side groups 15, of silane hydride 17, or of vinyl silane 18, which can react with silicone coatings in a hydrosilation reaction. The rest compatible with the coating is preferably an oligomeric or polymeric hydrocarbon 16 or a polysiloxane 19, which can improve the adhesion of the silicone layer by physical mixing and bonding.

The remainder 14 is typically compatible with the substrate if the substrate comprises the same groups or groups similar to said residue. For example, the moiety 14 comprising hydrophilic groups is typically compatible with the hydrophilic substrate. Usually, the rest with, for example, O or N atoms is hydrophilic. Similarly, the moiety 14 comprising hydrophobic groups is typically compatible with the hydrophobic substrate. Usually, the rest with, for example, hydrocarbons is hydrophobic.

The functional chemical substance comprises a polymeric main chain. The polymeric main chain is preferably water soluble or water dispersible. It can be selected, for example, from the group of vinyl polyalcohol, polyethylene glycol, ethylene polyoxide, polyvinylamine, starch, starch ester, starch ether, carboxymethyl cellulose, carboxymethyl cellulose ether, carboxymethyl cellulose ester, chitosan, xanthan, or polyacrylamide. The polymeric main chain is preferably vinyl polyol or starch.

The functional chemical substance preferably comprises double bonds that can react with the silicone coating. Advantageously, at least some double bonds are located at the end of the side chains of the main polymer chain.

The typical substrate for a release coating is paper, for example glass paper. Crystal paper refers to a paper that is made of chemical pulp and whose weight is typically 50 to 150 g / m2. Typically a good transparency of the glass paper is required; for a paper of 60 g / m2, it is typically at least 45, measured with visible light (ISO 2469: 1994). In the manufacture of glass paper, the pulp is finely ground so that it

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achieves a dense, substantially non-porous role. Because crystal paper is used as the base paper for release paper, a pore-free superfine is a requirement for good siliconization capacity. The surface without pores can be achieved with calendering treatments and surface treatment. The paper can be calendered first and then it can be treated superficially, or first it can be treated superficially and then it can be calendered. The calender could be a calender of multiple contact lines between rollers, or a supercalandria. In the calender, at least one contact line between rollers is formed between a hard surface roller and a smooth counter surface.

After applying the functional chemical substance on the base paper, the paper can be siliconated. The hydrosilation reaction takes place between the reactive functional chemical substance layer and the reactive groups of the silicon-containing release agent on the functional layer. In this way, a firm bond is formed between the paper and the coating.

The following examples describe the formation of the functional layer on the surface of the paper, and also how the removal of silicone by rubbing can be suppressed using the layer of functional chemical substance between the base paper and the silicone coating.

Example 1

The steam applicator (HU Jakob Papiertechnik AG, Switzerland) was evaluated on a production scale by applying steam and dissolution of functional chemical substance (PVOH-C5-s-5%) to a supercalandria. The polymeric main chain of PVOH-C5-s-5% is a vinyl polyol with a degree of hydrolysis of 98%. Nominally, 5% of the polymer hydroxyl groups are grafted with a side chain comprising 5 carbons and a double bond at the end of the side chain. The steam applicator was mounted between the unwind station and the first roller contact line of the supercalandria.

The speed of the supercalandria was constant during the tests (approx. 610 m / min.), And also the vapor pressure was kept as constant as possible (around 1 bar). The temperature of the value was approximately 90 ° C. The amount of the solution of functional chemical substance (liters / hour) was increased during the test in order to increase the weight of the coating. The concentration of the solution was approximately 3% by weight.

The samples were coated with silicone after the supercalandria in the laboratory liner. The silicone (Rhodia 3) was applied with a blade, and cured immediately after coating. Next, the samples were stored in a humidity chamber (T = 50 ° C, RH 75%), and the removal of silicone by rubbing was evaluated as a function of time. Acrylic tape was used, because it usually increases the risk of earlier removal of the silicone layer by rubbing.

Results

Three different amounts of functional chemical substance were applied on the glass paper. Table 1 shows the numbers of the test points and the consumption of the solution of the functional chemical substance. The theoretical maximum amount of the functional chemical substance was also calculated. Actually, the amount is less than the calculated value, because the entire solution does not stick on the surface of the paper.

Table 1. Three different quantities of functional chemical substance were applied on the glass paper: the numbers of test points, the consumption of the solution of functional chemical substance, and the maximum theoretical amount of the

functional chemical substance.

 Test point

 Dissolution consumption (l / h) Maximum coating weight (g / m2)

 Reference to

 0 0

 KP 5

 20 0.02

 KP 6

 30 0.03

 KP 7

 50 0.05

The results of rubbing removal are shown in Table 2 as a function of time. In the reference sample A, rubbing removal is observed after 2 weeks. The differences between reference A and samples with lower coating weights were not obvious. In the sample that theoretically contains 0.05 g / m2 of the functional polymer, no rubbing removal was observed during the test period.

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Table 2. The rub-off results for the reference and for the samples containing the functional polymer as a function of time (1 = good quality, without rub-off elimination; 2 = rub-off elimination; and 3 = elimination by noticeable rubbing). All samples were stored in a humidity chamber (a refers to the area without tape, and b to the area under acrylic tape).

 0 h 2 weeks 3 weeks 4 weeks 6 weeks 8 weeks

 Sample

 a a b a b a b a b a b

 Reference to

 1 1 2 1-2 3 2 3 2 3 2 3

 KP 5

 1 1 1 1 2 1 2 1 3 1 3

 KP 6

 1 1 1-2 1 2-3 1 3 1 3 1 3

 KP 7

 1 1 1 1 1 1 1 1 1 1 1

Example 2

The test was carried out as in Example 1, but in this experiment the steam applicator was also attached to the paper machine just before the moisturizing unit.

Results

Three different amounts of functional chemical substance were applied on the glass paper. Table 3 shows the numbers of test points and the consumption of the functional chemical substance solution. The theoretical maximum amount of functional chemical substance was also calculated. Actually, the amount is less than the calculated value, because the entire solution does not stick on the surface of the paper.

Table 3. Three different quantities of functional chemical substance were applied on the glass paper: the test point numbers, the consumption of the functional chemical substance solution, and the theoretical maximum amount of

lining material

 Test point

 Dissolution consumption (l / h) Maximum coating weight (g / m2)

 Reference B

 0 0

 KP 1

 20 0,024

 KP 2

 40 0.048

 KP 3

 50 0,060

Table 4 shows the results of rub removal as a function of time. In the reference sample B, rubbing removal is observed after 2 weeks. The differences between reference B and samples with lower coating weights were not obvious. The sample that theoretically contains 0.06 g / m2 of the functional polymer had a clearly improved anchor compared to the reference.

Table 4. The results of rubbing removal for reference and for samples containing the functional polymer as a function of time (1 = good quality, no rubbing removal; 2 = rubbing removal detected; and 3 = removal by noticeable rubbing). All samples were stored in a humidity chamber (a refers to the area without tape, and b to the area under acrylic tape).

 0 h 2 weeks 4 weeks 6 weeks 8 weeks

 Sample

 a a b a b a b a b

 Reference B

 1 1-2 2 1-2 3 2 3 2 3

 KP 1

 1 1-2 1-2 1-2 2 1-2 3 1-2 3

 KP 2

 1 1 1-2 1 1-2 1 2 1-3 3

 KP 3

 1 1 1 1 1 1 1-2 1 1-2

The difference between the coating weights in example 1 and in example 2 results from the different location of the steam application beam.

In summary, the process according to the invention to form the layer of functional chemical substance using a steam applicator technology allows the application of a very low coating weight (approx. 0.05-0.06 g / m2), and when The functional chemical substance is applied just on the outermost surface of the glass paper, the elimination of silicone by rubbing can be avoided.

Claims (16)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 1. Method for treating a surface of a substrate, said method comprising applying a functional chemical substance on the surface of the substrate to improve the adhesion of the silicone to said substrate, wherein the method comprises: - applying said functional chemical substance in an amount of at least 5 mg / m2 on the substrate surface using a vapor application beam to form a layer of functional chemical substance on the substrate, said functional chemical substance comprising double bonds, silane hydride, or vinyl silane reactive groups, or oligomeric or polymeric hydrocarbon or polysiloxanic compounds. 2. Method according to claim 1, characterized in that the functional chemical comprises vinyl groups. 3. Method according to claim 1 or 2, characterized in that the functional chemical comprises a main chain having one or more side chains, in which at least some double bonds are located at the end of said side chains of said chain principal. 4. Method according to any of the preceding claims, characterized in that the functional chemical is applied in an amount of approximately 0.05 g / m2 on the surface of the substrate. 5. Method according to any of the preceding claims, characterized in that the functional chemical substance is applied on the surface of the substrate in water in the form of a solution, a dispersion or an emulsion. 6. Method according to any of the preceding claims, characterized in that the functional chemical is applied on an uncoated substrate. 7. Method according to any of the preceding claims, characterized in that the functional chemical substance is applied on a previously coated substrate. Method according to any of the preceding claims, characterized in that the functional chemical substance is applied on a calendered substrate. 9. Method according to any of the preceding claims, characterized in that the substrate is made of paper. 10. Method according to claim 9, characterized in that the substrate is made of glass paper. 11. Method according to any of claims 1 to 8, characterized in that the substrate is made of a film material. 12. Method according to claim 11, characterized in that the substrate is made of a thermoplastic polymeric material, advantageously ethylene polyterephthalate (PET), oriented polypropylene (OPP), low density polyethylene (LDPE), or high density polyethylene (HDPE) ). 13. Method according to any of claims 1 to 12, characterized in that the method further comprises applying said silicone coating on said substrate. 14. Release coating comprising a substrate and a silicone layer on the surface of the substrate, wherein the substrate is treated with the method according to any of the preceding claims. 15. Release coating according to claim 13, characterized in that the substrate is made of glass paper. 16. Release coating according to claim 13 or 14, characterized in that the substrate is calendered before or after the treatment with the method according to any of claims 1 to 10.